1. Field of the Invention
The present invention relates, in general, to a method for forming contact holes of a semiconductor device and, more particularly, to a method for forming contact holes with a size of not more than the resolution limit by a sacrificial film spacer technique which results in an improvement in the operating reliability of semiconductor devices and the production yield as well as the high integration of devices.
2. Description of the Prior Art
High integration of semiconductor devices forces contact holes, which interconnect lower and upper wirings or capacitors, to be reduced in size. The distances between contact holes and peripheral wirings are required to be reduced, as well. In contrast, the aspect ratio of contact holes, the ratio of diameter to depth, is increased. Thus, an accurate and strict arrangement of contact holes should be constructed in the semiconductor devices in which multilayer conductive wirings are formed, with reduced process allowance. Reduction of contact holes in size requires semiconductor device manufacturing apparatuses to be more precise. With current apparatuses, it is very difficult to form fine patterns having a size of, for example, 0.4 .mu.m or less.
In order to make the contact holes distant from one another, they should be formed according to a certain design rule between contact hole masks in consideration of the following factors: first, misalignment tolerance upon mask arrangement; second, lens distortion upon light exposure process; third, critical dimension variation upon mask manufacture and photolithography; and fourth, registration between the masks.
It is very difficult to highly integrate devices because the above consideration factors seem highly likely to force the size of contact holes themselves and the distance therebetween to be increased over the limits of the resolution of photoresist film patterns.
In addition, since the distance between conductive wirings should also be formed in consideration of the overlapping with the contact holes, the width of the conductive wirings as well as the distance increases and thereby serves as a factor to make the high integration of devices difficult.